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Re: it isn't strange?!

  • To: mathgroup at smc.vnet.net
  • Subject: [mg116133] Re: it isn't strange?!
  • From: DrMajorBob <btreat1 at austin.rr.com>
  • Date: Thu, 3 Feb 2011 05:29:01 -0500 (EST)

I will assume that "pb" means peanut butter.

So here is your peanut butter:

conditions =
  Reduce[Max[a, b] == Max[c, d], c, Reals] /. {And -> List, Or -> List}

{{d < Max[a, b], c == Max[a, b]}, {d == Max[a, b], c <= Max[a, b]}}

conditions /. {d -> 2, a -> 4, b -> 3, c -> 6}
And @@@ %

{{True, False}, {False, False}}

{False, False}

conditions /. {d -> 4, a -> 4, b -> 3, c -> 6}
And @@@ %

{{False, False}, {True, False}}

{False, False}

A tautology is a logical statement that's true for every value of the  
variables.

Your conditions are NOT a tautology, as your two examples prove.

Bobby

On Wed, 02 Feb 2011 05:06:39 -0600, olfa <olfa.mraihi at yahoo.fr> wrote:

> Hi Mathematica community,
>
> here is my pb:
>
>  input:
> Reduce[Max[a, b] == Max[c, d], c, Reals]
> output:
>  (d < Max[a, b] && c == Max[a, b]) || (d == Max[a, b] &&  c <= Max[a,
> b])
>
> when testing this output with 2 initialisations:
> d = 2  a =  4  b = 3  c = 6  here d < Max[4, 3] but c is not equal to
> Max[4, 3]
>
> d = 4  a =   4  b = 3  c = 6  here d = Max[4, 3] but c is not <= to
> Max[4, 3]
>
> where is the pb?!
>


-- 
DrMajorBob at yahoo.com


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